Method and apparatus for forming metal screw blanks



March 28, 1939.

H. KOESTER 2,151,776

METHOD AND APPARATUS FCR FORMING METAL SCREW BLANKS r--- 58 1 5 7 l I32* l 31 5:;- .96

| E 24 I v I Filed Jan. 31, 1938 J= 3 w J 1 l .97 l 35 23 36 I t 36 2.9.l I 34 1 30. I l A INVENTOR. HERMAN K055 TERI ATTORNEY.

Patented-Mar. 23, 1939 METHOD AND APPARATUS FOR FORMING, METAL SCREWBLANKS Herman Koester, Waterbury, Conn., assignor to The BristolCompany, Waterbury, Conn., a corporation of Connecticut ApplicationJanuary 31, 1938, Serial No. 187,784

9 Claims.

a solid cylindrical blank of metal with an enlargement at one end,forming a socket in the enlargedend, and forcing the blank by an angularor noncircular punch through a die opening that is smaller in diameterthan the enlarged end of the blank, thereby drawing the metal of thatportion onto the punch and causing the interior contour of the socket toconform to the exterior contour of the punch. Such a method is set forthin U. S. Letters Patent No. 960,244, issued to W. G. Allen, June 7,1910. From a study of the principles-involved, it will be apparent thatin this method the operation by which the socket is caused to assume itsfinal form is in the nature of a drawing action, whereby, during theforming process, the fibres of tne metal are in a state of tension, witha resultant tendency to inherent weakness of the finished product at apoint where, under conditions of use, it is likely to be submitted torelatively great stresses.

Another process involves theuse of a noncircular punch which enters theoriginal socket in the blank, the tip of the punch engaging the bottomof the socket and forcing the metal into a cylindrical mold with agenerally radial flow,

7 the walls of the mold serving to restrict the flow until it closes inupon the punch. In this process,

as in the former, the final conformation of the blank is effected byforce applied to the metal by the tip of the punch, from which action isinseparable a certain splitting, shearing, or drawing tendency, by whichthe fibres of the metal are placed in a state of tension.

It is an object of this invention to provide a method and apparatus forforming screw blanks of the nature set forth, in which the final formingoperation, including the conformation of the interior of the socket tothe desired contour,

from blanks formed according to this process,

when tested under controlled conditions, show a resistance to breakingas much as fifteen percent higher than similar screws made from blanksof the same material formed by different methods.

It is proposed to accomplish the desired result by providing for use ona heading machine of the conventional type a forming member embodyingtwo distinct sections-a longitudinally yielding mandrel adapted to entera previously formed recess in a blank, and having its contour formed tothe desired cross-section of the socket, and an annular portionsurrounding said mandrel and having a substantially fiat face smaller indiameter than the previously enlarged portion of the blank, and adaptedto engage the same, extruding it solely by compression through a dieaperture of substantially the same diameter as that of the annularportion of the forming member.

The nature of the invention, however, will best be understood whendescribed in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation of a blank of uniform diameter, as cut fromsuitable bar or wire stock.

Fig. 2 is a side elevation, partially in section, showing the first stepin the upsetting or heading process.

Fig. 3 is a similar view, showing the second step in the headingprocess.

Fig. 4 is a similar view showing the initial step in forming the socket.

Fig. 5 is a side elevation, partially in section, of the combinedextrusion member and mandrel, and of the die through which the blank isfinally extruded, showing said. parts of the mechanism in the positionof initial engagement with the blank.

Fig. 6 is a similar view showing the flat-faced extrusion member andenclosed mandrel in engagement with the blank and having forced it partway through the die.

Fig. '7 is a similar view of the engaging parts of the punch, mandreland die, showing said parts in the position of final engagement with theblank after extrusion through the die.

Referring to the drawing, a blank l0, Fig. 1, of suitable length anduniform cylindrical crosssection is first cut off from rod or wirestock. This blank is next upset to form a head thereon, which action iseffected in two upsetting operations, bringing the blank successivelyinto the forms shown in Fig. 2 and Fig. 3. While this part of theprocess presents no particular novelty, and for it no invention isclaimed, yet, in order that there may be had a clear understanding ofthe whole process of forming the screw blank, it is outlined briefly asfollows:

The blank I0 is inserted in a lower die ll above a conventionalknock-out pin l2 closely fitting an axial aperture l3 of the samediameter as that of the blank [0. (It will be understood that in thisdescription the terms upper, lower, etc., are purely relative, and thatthe process may be carried out as effectively in a machine havinghorizontally disposed die parts as in one wherein those elements arevertically disposed.) The upper end of the-blank in this positionprojects through a die cavity l4 formed in the upper face of the die llcoaxial with the aperture l3 and having its outer surface I5 conformedto a truncated cone and its bottom surface 16 departing slightly from atrue fiat into a. conical conformation rising toward the center, andforming in the contour line of the section of the die an acute anglewith the cylindrical surface of the aperture [3.

Cooperating -with the lower die H is an upper movable die l1 having inits workingface a tapered aperture l8 adapted to receive the projectingend of the blank before and during the initial upsetting step. Thus,when the die I1 is brought down upon the die H with sufficient force,there will be formed upon the blank a relatively wide-bottomed upsetportion l9, projecting slightly over the conical surface l6, but notcompletely filling the cavity Hi, the whole blank now having the formshown at Ina.

After the blank has been shaped as described, it is next shaped into theform shown at lllb, Fig. 3, this being effected by the die ll, carryingthe partially upset blank, being brought into operative relationshipwith a die 20 having in its working face a recess 2| in the form of ashallow truncated cone of maximum diameter substantially the same asthat of the recess I4 in the die ll. When the dies 20 and II are broughttogether, the upset portion I9 on the blank Illa will be caused to fillcompletely the recesses l4 and 2|, resulting in the formation on theblank of a head having a contour as indicated in Fig. 3, and adapted forthe initial step in forming the socket.

After having been shaped to the conformation shown at lllb in Fig. 3,the blank may, if desired, be annealed, it then being transferred to adie 22 as shown in Fig. 4. The die 22 is similar to the die H, but thecavity therein is made slightly deeper than the cavity M by the additionof a short cylindrical portion asat 23, to accommodate the axial flow ofmetal attending the punching of the recess later to be developed into asocket. A punch member 24, having a cylindrical tip portion, preferablywith a rounded end, is then brought into engagement with the fiattenedtop of the blank, and forced thereinto to a distance predetermined byadjustment, thus forming a recess 25 of a depth less than the desiredultimate depth of the socket, and of a diameter substantially equal tothe maximum desired diameter of the finished socket. In this step of theprocess, the fiow of metal in the direction of punching being preventedby the presence of a knock-out pin 26, and lateral flow by the walls ofthe die cavity, the metal has no alternative but to flow backwards alongthe punch in a generally axial sense, filling the short cylindricalspace 23, resulting in a recessed blank as shown at 100, having a headportion of axial length slightly greater than that of the head beforerecessing. The flow of the metal solely in a direction longitudinal of,and in opposition to, the movement of the punch has been found toproduce a molecular condition which results in a blank better suited toformation by, and producing a stronger ultimate product after, theextrusion process now to be set forth, than is obtainable in blankshaving a recess punched with restriction as to the outward radial flowof the metal.

The final forming of the blank is effected by a combination of formingtools shown in detail in Fig. 5. These comprise a die member 21 havingformed therein an aperture with a smoothly tapered entrance portion 28of maximum diameter somewhat greater than the minimum diameter of thelower part of the conical head on the blank I00, and a cylindricalportion 29 of diameter equal to the desired final diameter of the headportion of the completed blank. Beneath the cylindrical portion 29 is acylindrical portion 30 of slightly greater diameter than that of portion29, relieved to permit free passage of the completed blank.

A forming tool 3!, adapted to coact with the die 21 in finally formingthe blank, is made up of two main portions, both adapted to engage thematerial of the blank during the forming process, but in such a manneras to segregate the nature of stresses exerted between these members andthe blank, the stress in the one member being wholly axial, and in theother wholly radial. To

' this end, the tool comprises a housing portion 32 which terminates inan extended annular extruding member 33 having an outside diametersubstantially the same as that desired for the head of the finishedblank, and adapted to pass through the aperture portion 29 in the die21.

Its inside diameter is substantially equal to the maximum desireddiameter of the final form of the socket to be formed in the blank.

Within the housing portion 32, extending through the annular member 33and free for limitedlongitudinal movement therein, is an extendedmandrel member 34 having a tip portion 35 which is provided with groovesor flutes 35, or is otherwise conformed to the contour and dimensions ofthe non-circular socket which it is desired to form in the blank. Thismandrel terminates in a head portion 36 positioned inwardly of thehousing portion 32, and is movable in a cylindrical chamber 31 formed inthe body thereof. A compression spring 38, contained within the chamber31, tends to maintain the mandrel member 34 in a position where tipportion 35 projects its maximum distance out of the annular extrudingmember 33, and to an extent not less than the maximum depth required forthe finished socket.

In the forming process, the blank I00, after again annealing if desired,is first positioned by a releasing grip (not shown in the drawing) inthe path of the tool 3|, which is then brought a into engagement withthe blank, carrying it into the die 21, as shown in Fig. 5. The strengthof the spring 38 is sufficient to assure positive seating of the tip ofthe mandrel 34 in the recess previously formed in the blank, but not toexert appreciable extruding force upon the blank as the latter entersthe tapered aperture portion 28 of the die 21. Consequently, as theheaded portion of the blank is definitely engaged by the tapered wallsof the aperture portion 28, both the blank and the mandrel member aremomentarily brought to rest, the spring 38 yielding as the housingportion 32 and the extruding member 33 continue to advance toward thedie 21.

As the annular flat faced extruding member 33 engages the flattened topportion of the blank, the latter is forced more deeply into the taperedaperture portion 28, the first wedging action on the sides of the headcausing. its metal to flow in such a manner that the walls of the recessgrip the tip portion 35 of the mandrel 34, and, as the blank continuesto be forced into the tapered portion of the die, to conform to theshape of the mandrel. The metal of the upper portion of the head willflow in upon the mandrel; and, as the diameter of the head becomeslessened withits passage through the narrow aperture portion 29, notonly will the flutes or other characteristic conformations of themandrel be completely filled with extruded metal, but the surplus metalattendant upon the reduction in cross-section of the head portion of theblank will be caused to flow in a generally longitudinal sense relativeto the mandrel, causing the head portion of 'the blank to be lengthened.The gripping action of the metal upon the tip of the mandrel, coupledwith the force of the spring 38, will prevent the mandrel being forcedback into the housing; and, as the metal of the blank is compressed orextruded toward the mandrel, the latter will ad- Vance at a higher ratethan the extruding member, so that as the head is built up and elongatedby the flowing metal, the socket will assume a depth greater than thatof the originally punched recess. This action, which is shown in Fig. 6.will continue until the blank has been forced all the way through thecylindrical portion of the lurgical characteristics of the originalblank, the

finished blank Ind may be caused to assume such dimensions that the baseof the head, originally containing a slightly conical recess, formed bythe part l6 of the blanking die, will assume a substantially flatconformation, as shown in Fig. 6, while the depth'of the finishedsocket, while greater than that of the original recess,w ill be slightlyless than the possible distance which the mandrel 34 may project fromtheannular ex truding member 33. The latter condition being fulfilled,the blank, immediately upon the head portion passing through thecylindrical-aperture portion 29, will be forced away from the extrudingmember 33 by action of the compression spring 38 forcing the mandrel 34to its extreme projected position, thus .leavinga slight space. as at39, between the annular face of the extruding member and the head of thecompleted blank, thus facilitating removal of the finished blank bymeans of automatic stripping mechanism (notshown in the drawing). Thusthere has been provided a method of and means for forming a screw blankby a process in which the metal is subjected only to an action in thenature of extrusion under. compression, rather than drawing undertension, and therefore is not at any time made subject to the weakeningstrains attendant upon forming the metal under conditions of tension or'outwardly exerted radial stress.

I claim:

1. Means for forming a socketed screw blank or the like from acylindrical blank with recessed head, comprising a die having therein anaperture with cylindrical section of diameter less than the diameter ofsaid blank and with a tapered section forming an approach theretoand-adapted to receive the blank, together with an annular extrusionmember adapted to engage said blank for forcing it through saidcylindrical section, and a coaxially disposed mandrel permanentlymounted in the extrusion member, movable axially thereto and adapted toproject beyond the same to enter the recess in said blank to an extentlimited by the bottom of the recess, the protruding terminal portion ofthe mandrel bearing peripheral conformations to impart a predeterminedcontour to the walls of said recess as the material of the blank islaterally compressed upon the said terminal portion under the action ofthe extrusion member.

2. Means for forming a socketed screw blank or the like from acylindrical blank with recessed head, comprising a die having therein anaperture with cylindrical section of diameter less than the diameter'ofsaid blank and with a tapered section forming an approach thereto andadapted to receive the blank,'together with an annu- .to project beyondthe same to enter the recess in said blank to the full extent of itsdepth, the

protruding terminal portion of the mandrel bearing peripheralconformations to impart a predetermined contour to the walls of saidrecess as the material of, the blank is laterally compressed upon thesaid terminal portion under the action of the extrusion member.

3. Means for forming a socketed screw blank or the like from acylindrical blank with recessed head, comprising a die having therein anaperture with cylindrical section of diameter less than the diameter ofsaid blank and with a tapered section forming an approach thereto andadapted to receive the-blank, together with an annular extrusion memberhaving an annular fiat pressure face of an outside diameter equalsubstantially to that of the finished head of the blank and an innnerdiameter equal substantially to that of the final form of the finishedsocket. said face being adapted to engage said blank for forcing itthrough 'said cylindrical section, and a coaxially disposed mandrelpermanently mounted in the extrusion member, movable axially theretoand. adapted to project beyond the same to enter the recess in saidblank to an extent limited bythe bottom of the recess, the protruded toreceive the blank, together with an annular extrusion member adapted toengage said blank for forcing it through said cylindrical section, anda. coaxially disposed mandrel portion mounted in the extrusion memberand adapted to project beyond the same to enter the recess in said blankto the full extent of its depth, longitudinally yieldable relatively tothe extrusion member, and having a protruding terminal portion' bearingperipheral conformations to impart a predetermined contour to the wallsof said recess as the material of the blank is laterally coming terminalportion of the mandrel bearing pepressed upon the said terminal portionunder the action of the extrusion member.

5. Means for forming a socketed screw blank or the like from acylindrical blank with recessed head, comprising a die having therein anaperture with cylindrical section of diameter less than the diameter ofsaid blank and with a tapered section forming an approach thereto andadapted to receive the blank, together with an annular extrusion memberhaving an annular fiat pressure face at one end adapted to engage saidblank for forcing it through said cylindrical section and the other endof said member being enlarged to afford a housing, a mandrel mounted inthe extrusion member coaxially therewith and longitudinally movablerelatively thereto, and resilient means mounted in the housing of theextrusion member bearing upon an end of the mandrel to extend itsopposite end beyond the flat pressure face, the protruding terminalportion being adapted to enter said recess and bearing longi tudinalflutes to impart a predetermined contour to the walls of said recess asthe material of the blank is laterally compressed upon the said terminalportion under the action of the extrusion member.

6. Means for forming a socketed screw blank or the like from acylindrical blank with recessed I head, comprising a die having thereinan aperture with cylindrical section of diameter less than the diameterof said blank and with a tapered section forming an approach thereto andadapted to receive the blank, together with an annular extrusion memberhaving an annular fiat pressure face at one end adapted to engage saidblank for forcing it through said cylindrical section and the other end'of said member being enlarged to afford a housing, a mandrel comprisinga rod passing through the extrusion portion of the extrusion member, itsprotruding tip bearing longitudinal flutes and adapted to enter saidrecess, the other end of the rod terminating in a head portion withinthe housing, and a compression spring within the housing bearing uponsaid head to cause said tip to protrude beyond the said extrusionmember.

7. In the manufacture of socketed screws or the like: the process offorming a socketed blank from a solid cylindrical blank with a recessedenlargement at one end, which comprises forcing the blank through acircular die openingsmaller than the enlarged end of the blank by applypressure thereto solely by means of the annular fiat face of a hollowextrusion member with outside contour equal substantially to thediameter of said opening; and, prior to the engagement of the annularflat face with the blank, introducing from the said hollow member intothe recess of said blank a mandrel portion of predeterminedconformation, the mandrel being free for axial movement relatively tothe extrusion member and exerting substantially no extrusion pressureupon the blank and the movement of said mandrel being temporarilyinterrupted with the extrusion member continuing through the die,whereby as the blank is forced through said die opening solely by theannular face of the extrusion member the metal of said enlarged portionof the blank is laterally compressed onto the introduced mandrelportion, and the recess in said enlargement is caused to assume acontour corresponding to the cross-section of the introduced mandrelportion and a depth independent of the axial dimension of saidmandrel. I

' 8. In the manufacture of socketed screws or the like: the process offorming a socketed blank from a solid cylindrical blank with a recessedenlargement at one end, which comprises forcing the blank through acircular die opening smaller than the enlarged end of the blank byapplying pressure thereto solely by means of the annular fiat face of ahollow extrusion member with outside contour equal substantially to thediameter of said opening; and, prior to the engagement of the annularflat face with the blank, yieldingly introducing from the said hollowmember into the recess of said blank a mandrel portion of predeterminedconformation and to the full depth of said recess, the mandrel exertingsubstantially no extrusion pressure upon the blank, whereby as thelatter is forced through said die opening solely by the annular face ofthe extrusion member the metal of said enlarged portion of the blank islaterally compressed onto the introduced mandrel portion, and the recessin said enlargement is caused to assume a contour corresponding to thecross-section of the introduced mandrel portion.

9. In the manufacture of socketed screws or the like: the process offorming a socketed blank from a solid cylindrical blank with anenlargement at one end, which comprises first punching a recess in theenlargement of the blank by punch and die means conformed to limit metalflow under the action of the punch to a direction substantially inopposition to the direction of the force applied to said. punch, forcingthe blank through a circular die opening smaller than the enlarged endof the blank by applying pressure thereto solely by means of the annularflat face of a hollow extrusion member with outside contour equalsubstantially to the diameter of said opening; and, prior' to theengagement of the annular fiat face with the blank, introducing from thesaid hollow member into the recess of said blank a mandrel portion ofpredetermined conformation, the mandrel being free for axial movementrelatively to the extrusion member and exerting substantially noextrusion pressure upon the blank and the movement of said mandrel beingtemporarily interrupted with the extrusion member continuing through thedie, whereby asthe blank is forced through said die opening solely by-.the annular face of the extrusion member the metal of said enlargedportion of the blank is laterally compressed onto the introduced mandrelportion, and the recess in said enlargement is-caused to assume acontour corresponding to the cross-section of the introduced mandrelportion and a depth independent of the axial dimension of said mandrel.

IERMAN KOESTER.

